1. Field of the Invention
The present invention relates generally to methods for making computer hard disk drive heads, and more particularly to methods for etching nickel iron plated thin films to form elements of a magnetic recording head.
2. Description of the Related Art
Thin films of nickel iron alloys are used to form elements of magnetic recording heads in computer hard disk drives. For example, thin Ni-Fe films may form pole pieces in a write head. One way to form thin film write head elements is to cover a thin film layer on a substrate with a monomer and expose to light those portions of the layer that are intended to establish the write elements. This transforms the monomer into a protective polymer film over the covered portions, and then the thin film layer can be bathed in an etchant to remove the portions of the layer that are not protected by the polymer film.
Many existing etching processes use hydrochloric acid as the etchant, particularly for thin films having an iron content of greater than 20%. The chloride in hydrochloric acid is very corrosive and thus is effective in reducing the desired portions of the thin film layer. As recognized by the present invention, however, the chloride can combine with thin film material so that the chloride continues to corrode the material during and long after manufacture. Unfortunately, the residual corrosive effect of chloride results in magnetic recording head failures and in increased manufacturing costs arising from the need to closely inspect thin film magnetic recording heads for continuing, undesirable chloride corrosion. The present invention recognizes that the phenomenon of residual chloride corrosion arises predominantly when the "final" surfaces of a magnetic recording head--i.e., the surfaces of the magnetic recording head that remain after etching--have been exposed to hydrochloric acid during etching.
Additionally, the present invention recognizes the desirability of providing a reproducible, reliable non-chloridic etchant. To this end, the present invention understands that the method disclosed in, e.g., German Patent No. 146627 is less reliably reproducible for large-scale manufacturing purposes.